I suspect propane in a pre-chamber diesel like MB's will cause serious pre-ignition unless injected with the fuel -- same reason it isn't very smart to use ether to help start one. I've tried it, it won't work -- ignites so early it stops the starter. Most American truck diesels are direct injection -- start fine on ether.

Propane will burn cleaner than diesel fuel for sure -- so will ethanol. Propane power is wonderful -- no soot in the oil, no deposits, vehicle runs forever. Probably does help the diesel burn cleaner, but I still wouldn't try it in an MB -- good way to break the ring lands.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!